ES3035815T3 - Tray conveyor driven by brushless dc motor - Google Patents

Abstract

A conveyor for transporting items, supported by trays with independent power supply and control. Each tray consists of a blade suspended from an item-supporting platform. A series of drive coils are integrated into the blade. A battery and controller integrated into the tray drive the coils. The blade slides in a slot between two conveyor rails that support the tray platform. The slot is delimited by an array of permanent magnets along each rail. The drive coils generate an electromagnetic field that interacts with the permanent magnetic field of the slot to form a brushless DC motor that drives the tray along the rails. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Tray conveyor driven by brushless DC motor

Background

The invention relates generally to motorized conveyors and, more specifically, to conveyors in which the trays are independently driven by brushless direct current (DC) motors.

Conventional conveyor systems, such as those that transport items on flat belts, modular belts, or chains, and driven or gravity-operated rollers, pose many sources of pathogens and other contaminants. Motors, gearboxes, roller bearings, shafts, pulleys, and sprockets can accumulate food particles and grease, requiring regular cleaning. In food applications, all conveyor parts must meet stringent food-grade standards. In addition, conventional conveyors require significant electrical infrastructure for power and control. Cable routing and connections represent additional sources of contaminants.

EP 0241 875 A2 discloses a solid-state commutated linear motor with an ironless multiphase armature having a magnetic field array with periodically alternating polarity, an ironless multiphase armature and a solid-state commutation system for driving a moving element and positioning it relative to a reference element.

JP 2004 015894 A discloses a linear motor composed of moving elements provided with a linear scale and a permanent magnet, a sensor for reading the scale and stators provided with a coil that generates a switchable magnetic field in the permanent magnet.

US 8829 740 B2 discloses a sealed linear motor system including a sealed coil assembly with a plurality of coil windings within a base plate and comprising covers disposed around the base plate and the coil windings to prevent ingress of moisture and/or chemicals into the base plate and the coil windings.

Summary

A conveyor according to the invention is described in the independent claim. Other aspects of the invention are described in the dependent claims.

Brief description of the illustrations

FIG. 1 is an isometric view of a portion of a tray conveyor incorporating the features of the invention.

FIG. 2 is an enlarged cross-section of the tray conveyor seen along lines II-II of FIG.

FIG. 1.

FIG. 3 is an enlarged cross-section of the tray conveyor seen along lines III-III of FIG. 1 with the inner wall of a support rail cut away to show a permanent magnet array.

FIG. 4 is an isometric view of a tray usable on the conveyor of FIG. 1 where the body of the tray is shown in virtual lines.

FIG. 5 is an isometric view of a portion of another version of a conveyor as in FIG. 1 with a conductive loop along both sides for inductively coupling the feed to the tray.

FIG. 6 is an enlarged cross-section of the conveyor of FIG. 5 viewed along lines VI-VI of FIG. 5.

FIG. 7 is a schematic block diagram of one version of an electrical system for a conveyor as in FIG. 5 or FIG. 1.

FIG. 8 is an isometric view of a tray carriage usable on a conveyor as in FIG. 1 or FIG. 5.

FIGS. 9A-9C are sequential isometric views of one end of a conveyor as in FIG. 5 using a tray car as in FIG. 8 to form an endless conveyor.

FIG. 10 is an isometric view of a tray washer for a conveyor as in FIG. 1 or FIG.

5.

FIG. 11 is an isometric view of a tray carriage as in FIG. 8 used to transfer trays from one conveyor segment to another.

FIGS. 12A-12C are sequential isometric views of a tray diverter section for a conveyor as in FIG. 1 or FIG. 5.

FIG. 13 is an isometric view of a lane cleaner on a conveyor as in FIG. 1.

FIG. 14 is an isometric view of a portion of another version of a conveyor as in FIG. 1 with a conductive loop shared by both sides to inductively couple power to the tray through a single secondary coil in the tray.

Detailed description

A portion of one embodiment of a conveyor incorporating features of the invention is shown in FIG. 1. Conveyor section 20 is comprised of a plurality of tray conveyor segments 22 connected end-to-end by bonded joints 24 to facilitate transitions. Also shown in FIG. 2, tray conveyor segments 22 each comprise a pair of proximate rails 26, 27 having convexly rounded tops 28, 29 and bottoms joined by a rail base 30 from which extends downwardly a leg 32 which braces on a floor surface. The two rails 26, 27 are separated by a narrow slot 34. A tray 36 has a platform 38 with an upper surface 40 holding the articles and an opposite lower surface 41 resting on the upper portions 28, 29 of the rails 26, 27. A scoop 42 extends downwardly from the lower surface 41 of the tray 36 in the slot 34. The tray 36 shown in this example with a centrally located scoop 42 forms a T in a vertical cross-section. A linear array of permanent magnets 44 in each rail 26, 27 produces a magnetic field across the slot 34 and the tray paddle 42. The magnitude and direction of the static magnetic field vary periodically along the length of the slot 34. Force coils (not shown in FIG. 1) in the tray paddle 42 produce a varying electromagnetic field which interacts with the magnetic field produced by the linear arrays of permanent magnets in the rail to create a force which drives the tray 36 along the conveyor in a conveying direction 46.

As shown in FIG. 2, the slot 34 located above the leg 32 extends upwardly from a lower blind end 48 formed by the base of the rail 30 to an upper opening 50 which widens at the upper portions 28, 29 of the rails 26, 27. Otherwise, the slot 34 is open at both the top and bottom. As shown in FIG. 3, the linear array of permanent magnets 44 is embedded in the rail 27 proximate an inner wall 52 of the rail bounding the slot 34. To increase the magnetic field strength in the slot 34, the permanent magnets 44 are shown arranged to form a Halbach array. The static magnetic field traversing the slot 34 varies spatially in amplitude and direction in the conveying direction 46.

As shown in FIG. 4, a plurality of force drive coils 54 are housed in the tray blade 42. The coils 54 are arranged in an alternating three-phase pattern along the length of the blade 42. A tray controller 56 housed in the tray 36 electronically switches currents through the three-phase coils 54 to produce an electromagnetic field that runs along the blade 42 and interacts with the static magnetic field in the slot. The controller 56 and auxiliary components are mounted on a circuit board 57. The cores of the coils 54 are iron-free to prevent attraction to the rail magnets and increased friction. The drive coils 54 thus form a brushless DC linear motor with the permanent magnet arrays in the rails. The permanent magnet arrays form the motor stator and the coercive tray coils 54 form the motor impeller.

A battery 58 comprised of one or more cells 60 powers the controller 56 and provides the switched currents to the coils 54. Because the permanent magnets are in the rails and the trays are battery operated, no wiring is needed in the tray conveyor segments. The tray segments are completely passive. Optional charging coils 62 are provided on one or both sides of the tray 36 to recharge the battery 58. Alternatively, the charging coils 62 could be used to couple power to the tray 36 to power the controller 56 and the force coils 54. In that alternate mode of operation, where primary power is inductively coupled to the tray 36 through the charging coils 62, the battery 58 can be used as a secondary power source when external power to the charging coils is not available. Thus, both the battery 58 and the charging coils 62 can serve as the tray's internal power source. When the primary external power source is active, the charging coils 62 can slowly recharge the battery 58. Calibration capacitors 64 are connected in parallel with the charging coils 62 to calibrate the charging coil and capacitor circuit to the resonant frequency of the external charging waveform to increase the efficiency of induced power transfer to the tray 36. As a third alternative, the battery 58 could be non-rechargeable and serve as the sole power source. In that case, the charging coils 62 and the calibration capacitors 64 would not be required. If the battery 58 is not rechargeable, it could be replaced by an end cap (66, FIG. 2), or the entire tray could be disposable.

When the charging coils 62 are used to recharge the battery 58 or as part of the primary power supply, one or more active segments of the conveyor 68 are used, as in FIGS. 5 and 6. Two closely spaced rails 70, 71 define a narrow slot 72 for receiving and guiding the paddle 42 of the tray 36. The rails 70, 71 each have side extensions 74, 75 with flat tops 76, 77 which support the tray 36. Primary conductor loops 78 powered by an alternating current (AC) power source (not shown) extend along the active section of the conveyor 68 on each rail extension 74, 75. The primary conductor loops 78 are mounted on E-cores 80. The conductor loops are, for example, low loss wires such as Litz wires. Primary gauge capacitors (not shown) are distributed around the loop along rails 70, 71 to provide highly efficient high Q inductive power transfer to the secondary charging coils 62 on tray 36. The bulk of the carrier may be constructed with active segments 68, as in FIG. 5, or with a combination of active segments and passive segments 22, as in FIG.

1. For example, a conveyor with a main guide rail along which items are transported and a return path could have passive segments on the guide rail and active segments for inductive power transfer on the return path to recharge the batteries. Alternatively, the active segment of the tray has a primary conductive loop on only one side. In that case, a tray could be manufactured with a secondary charging coil and a calibrating capacitor on only one side.

Another tray loading or feeding arrangement is shown in FIG. 14. In this version, tray 180 has a single loading coil 62 located in the center and connected in parallel with two calibrating capacitors 64. Although two calibrating capacitors 64 are shown, a single calibrating capacitor could be used instead. In this version, a primary conductor loop is formed by a left conductor segment 182 on a left rail 184 connected to a right conductor segment 183 on a right rail 185. The endless primary conductor loop is calibrated to resonate with one or more calibrating capacitors (not shown) and is powered by an alternating current (AC) source (not shown). This version can be used with rails without side rail extensions.

A version of a schematic diagram of the electrical block of a conveyor as in FIG. 1 or FIG. 5 is shown in FIG. 7. The tray controller 56 of this example is powered by an external AC source 82 or the battery 58. When the external source 82 is available, its energy is inductively coupled to the tray from the primary conductor loop 78 to the secondary charging coil 62. Calibrator capacitors 84, distributed along the loop 78, and the tray calibrator capacitor 64 calibrate the primary and secondary circuits to resonate at the frequency of the AC source 82 to maximize power transfer. The secondary AC voltage is converted to DC by a rectifier or AC-to-DC converter 86 whose output is a diode ORed with the battery voltage 92 through a diode 94 to produce a DC supply voltage 88 that powers the tray. Typically, the externally supplied voltage will exceed the voltage of battery 92 and power the tray controller 56 and other active devices on the tray. The battery 58 is activated to power the tray when the externally supplied voltage drops below the voltage of battery 92. When the external voltage exceeds the voltage of battery 92, it charges the battery 58 through a charging element 96. The ORed diode arrangement constitutes a rudimentary switch that switches between external power and battery power for the tray. An exemplary alternative switch useful for switching from external power to battery power includes an electromechanical or electronic switch that connects the DC supply voltage 88 of the tray to the voltage of battery 92 from the externally supplied DC voltage when the external power is too low. A low voltage detector that detects the incoming AC voltage or its rectified DC voltage sends a low voltage signal to the switch to switch to battery power.

An array of magnetic field sensors 98, such as Hall effect sensors arranged periodically along the tray paddle 42 (FIG. 4), determine the position of the tray coils 54 relative to positive and negative peaks in the magnetic field. The signals from the sensor 99 are sent to the controller 56, which includes a switch 100. The switch 100 is a software routine running in the program memory of the controller 56, e.g., a microcomputer or microcontroller. The switch 100 generates three output signals 104, which are properly in phase as determined by the signals from the sensor 99, to control the current through the three-phase force coils 54. The three output signals 104 are amplified by amplifiers 102 which supply the switched current waveforms to the force coils 54 to drive the tray.

The tray controller 56 of each tray communicates with a conveyor controller 106 external to the trays. A transceiver 108 on the tray circuit board 57 is wirelessly linked via antennas 110, 111 to an external transceiver 109 connected to the system controller 106. The system controller 106 sends command requests and data to the tray controllers 56 via the wireless link and receives data from the tray controllers. The tray antenna 110 is shown in FIG. 4 as a dipole integrated into the tray platform 38 along one end of the tray 36, by way of example.

A tray carriage 112 is shown in FIG. 8 and is used to transfer trays from one conveyor segment to another. The carriage 112 is the same as the trays described above, but with a pair of passive transfer rails 114, 115 mounted on the top surface 116. Like the tray rails 26, 27 of FIG. 2, the transfer rails 114, 115 have permanent magnet arrays disposed along their length. The narrow slot 118 between the transfer rails 114, 115 extends in length perpendicular to the plane of the carriage paddle 120.

FIGS. 9A-9C illustrate how carriage 112 transfers trays from one conveyor segment 68 to another 68'. A tray 36 advances along a first conveyor segment 68 at one end of a first conveyor path and is received in transfer rails 114, 115 of carriage 112. Carriage 112 is supported by a carriage conveyor segment 122 that extends perpendicular to the planes of slots 72 of first and second conveyor segments 68, 68'. The carriage conveyor segment 122 is below the level of the tray conveyor segments 68, 68' so that the transfer lanes 114, 115 are level with the tray conveyor lanes 70, 71. In this way, the transfer lanes 114, 115 and transfer slot 118 can be aligned with the tray coils 70, 71 and the tray slot 72 on the first tray conveyor segment 68 to smoothly receive the tray 36, as can be seen in FIG. 9A. Once the tray 36 comes to a complete rest on the carriage 112, it comes to a self-stop. The carriage 112 energizes its drive coils and propels itself and propels the tray 36 laterally in a transverse direction 116, as shown in FIG. 9B , along the carriage conveyor segment 122. The carriage conveyor segment 122 has permanent magnet carriage rails 124, 125 and a carriage slot 126 like the tray conveyor segments. The carriage segment 122 has a leg 118 shorter than the tray conveyor segment to position the top surface 128 of the carriage segment 122 inclined perpendicularly and below the tops 76, 77 of the conveyor segments 68, 68'. When the carriage 112 reaches a position where its transfer rails 114, 115 are aligned with the tray rails 70, 71 of the second tray conveyor segment 68', as shown in FIG. 9C, the carriage 112 stops and the tray 36 is activated to advance off the transfer lanes 114, 115 and onto the aligned conveyor segment rails 70, 71 on the second conveyor segment 68'. With an identical carriage conveyor segment at the opposite end of the two tray conveyor sections, an endless tray conveyor is formed. The carriage 112 then returns to the first conveyor segment 68 to receive the next tray.

A tray washer 130 is shown in FIG. 10 covering a portion of the return path 132 in an endless conveyor 134 configuration. A segment of the cart conveyor 122 is shown at one end of the endless conveyor 134 where trays 36 are transferred from a guide rail 133 to the return path 132. The tray washer 130 includes spray nozzles and brushes for cleaning, rinsing, sanitizing, and drying the trays 36.

As shown in FIG. 11, the carriage conveyor segment 122 may be used to transfer the trays 36 between multiple conveyor sections 136A, 136B, 136C, 136D. The four tray conveyor sections are arranged parallel to each other, two on each side of a space 138 through which the carriage 112 travels perpendicular to the tray conveyor sections 136A-D.

The conveyor configuration of FIGS. 12A-12C has two tray conveyor segments 140A, 140B in-line across a space 142. A third tray conveyor segment 140C extends obliquely away from the space 142. The obliquely oriented conveyor segment 140C provides a deflection path for the trays 36 away from a straight path in the in-line conveyor segment 140B. A diverter carriage segment 141 includes a diverter carriage 144 which is located in the space 142. Diverter rails 146, 147 with integral permanent magnet arrays selectively align with the rails of the in-line tray conveyor segments 140A, 140B or with the oblique tray conveyor segment 140C. The diverter carriage 144 includes a post 148 extending downwardly from the rails 146, 147 to a diverter carriage platform 150, which rests on a cylindrical diverter base 152. The base 152 houses a ring of permanent magnets that creates a magnetic field directed radially from the periphery of the base. The diverter carriage platform 150 has side skirts 154 extending downwardly around the perimeter of the diverter base 152. Diverter carriage drive coils (not shown) disposed in the skirts and actuated by a diverter controller (not shown) on the diverter carriage 144 produce an electromagnetic field that interacts with the permanent magnet magnetic field of the base 152 to rotate the diverter carriage 144 between an in-line pan passing position, as in FIGS. 12A and 12B and an oblique tray diverting position, as in FIG. 12C. The diverter carriage segment 141 may be used to merge products from the tray segments 140B, 140C into the tray segment 140a as the trays 36 advance in the direction opposite to that of the arrows in FIG. 12C.

A lane cleaner 160 is shown in FIG. 13 cleaning a section of tray conveyor 162. Cleaner 160 has a housing 164 that encompasses water, cleaner, and sanitizer reservoirs (not shown).

The housing 164 is mounted on a base (not shown), such as a conveyor pan with a drive spool paddle that fits in the slot 166 between the two rails 168, 169 and propels the cleaner 160 along the conveyor section 162. One or more nozzles 170 spray the water, cleaner, or disinfectant onto the rails 168, 169. The outer rotating brushes 172 and an inner rotating brush 173 are mounted on a shaft 174 retained at its ends by arms 176 attached to the cleaner housing 164. The outer rotating brushes 172 have bristles on at least one inner side for cleaning the outer sides of the rails 168, 169. The inner brush 173 slides in the slot 166 and has bristles on both sides for cleaning the inner walls of the rails 168, 169.

Claims (10)

1. A conveyor comprising: a rail (26, 27) having an integrated permanent magnet array (44) and extending along the rail (26, 27) to form a permanent magnet stator creating a magnetic field; a tray (36) supported on the rail (26, 27) and having an upper article-supporting surface (40) and a plurality of commutated drive coils (54) as a force device acting with the stator of the permanent magnets to form a brushless linear DC motor for propelling the tray (36) along the rail (26, 27); a tray conveyor segment (22) extending from a first end to a second end in a conveying direction (46) and including: a pair of rails (26, 27) closely spaced and separated by a slot (34) and having tops (28, 29), each of the rails (26, 27) including an array of permanent magnets (44) that creates a magnetic field across the slot (34); where the tray (36) includes: a platform (38) forming the upper article-supporting surface (40) and a lower surface (41) resting on the upper portions (28, 29) of the rails (26, 27); a blade (42) extending downwardly from the bottom surface (41) and in the transport direction (46) to move in the slot (34) and housing the series of switched drive coils (54); a tray controller (56) that drives the drive coils (54) to produce a traveling electromagnetic wave that interacts with the magnetic field to drive the tray (36) in the transport direction (46); where the slot (34) widens at the upper parts (28, 29) of the rails (26, 27) and the upper parts (28, 29) of the rails (26, 27) are convexly curved. 2. A conveyor according to claim 1, wherein a) the drive coils (54) are three-phase coils, the tray controller (56) switches current through the three-phase coils (54) to form the brushless DC linear motor with the permanent magnet arrays on the rails (26, 27); or b) the drive coils (54) are three-phase coils, the tray controller (56) switches current through the three-phase coils to form the brushless DC linear motor with the permanent magnet arrays on the rails (26, 27), and wherein the tray (36) includes sensors on the paddle (42) that detect the magnitude of the magnetic field and send sensor signals to the tray controller (56) to switch the current. 3. A conveyor according to claim 1, wherein the drive coils (54) have iron-free cores. 4. A conveyor according to claim 1, further comprising a primary conductive loop (78) external to the tray (36) and extending in the transport direction (46) along the rails (26, 27) and wherein the tray (36) further includes a secondary coil (62) inductively coupled to the primary conductive loop (78) to supply power to the tray (36) while it is along the rails (26, 27). 5. A conveyor according to claim 4, wherein the tray (36) includes a battery (58) for powering the tray controller (56) and the series of drive coils (54) and wherein the battery (58) is recharged through the secondary coil (62). 6. A conveyor according to claim 1, further comprising a rail base (30) joining the rails (26, 27) and forming a closed end of the slot (34) and a series of individual legs (32) extending downwardly from the base (30) to mount the conveyor on a floor surface. 7. A conveyor according to claim 1, further comprising: a carriage conveyor segment (122) similar to the tray conveyor segment, but arranged with carriage rails (124, 125) and a carriage slot (126) perpendicular to and inclined below the rails and the slot of the tray conveyor segment; a car (112) that includes: a carriage platform supported on the upper parts of the carriage rails (124, 125); a carriage blade (120) extending downward from the carriage platform running in the carriage slot (126); a series of carriage drive coils on the carriage blade; a pair of transfer rails (114, 115) closely spaced apart, separated by a transfer slot (118) and extending upwardly from the carriage platform to the highest level with the tops of the rails on the tray conveyor segment for receiving or discharging a tray from the tray conveyor segment; a carriage controller that drives the carriage drive coils to produce a traveling electromagnetic wave that interacts with the magnetic field in the carriage slot (126) to drive the carriage (112) along the carriage conveyor segment (122) in a transverse direction (116) from a first position in which the transfer rails (114, 115) are aligned with the rails of the tray conveyor segment to a second position in which the transfer rails are transversely offset from the rails of the tray conveyor segment. 8. A conveyor according to claim 1, further comprising: a plurality of tray conveyor segments (140A, 140B, 140C) in which a first tray conveyor segment (140C) extends obliquely from the first end of a second tray conveyor segment through a space (142); a diverter carriage segment (141) having a cylindrical diverter base (152) housing a ring of permanent magnets that create a magnetic field around the periphery of the diverter base; a diverter car (144) including: a diverter carriage platform (150) supported on the diverter base (152) and having side skirts (154) extending downwardly around the periphery of the diverter base (152); a series of diverter carriage drive coils on each of the side skirts (154); a pair of closely spaced diverter rails (146, 147) separated by a diverter slot and extending upwardly from the diverter carriage bed to the highest level of the tops of the rails on the first and second tray conveyor segments (140A, 140B, 140C) for receiving or discharging a tray from the tray conveyor segment; a diverter carriage controller that drives the diverter carriage drive coils to produce a traveling electromagnetic wave that interacts with the magnetic field around the diverter base (152) to rotate the diverter from a first position in which the diverter rails align with the rails of the first tray conveyor segment to a second position in which the diverter rails align with the rails of the second tray conveyor segment. 9. A conveyor according to claim 1 further comprising a cleaner (160) including: a blade that slides in the slot (166); a series of wiper coils housed in the blade; a cleaner controller that drives the cleaner coils to produce a traveling electromagnetic wave that interacts with the magnetic field to propel the tray along the tray conveyor segment; a supply of cleaning solution; a spray nozzle (170) that sprays the cleaning solution onto the rails. 10. A conveyor according to claim 9, wherein the cleaner further includes rotating cleaning brushes (172, 173) that run in the slot (166) and along the outer sides of the rails to clean the rails.